>arr_months[0][0]=31;
How do you know his month is begining from January!?
Why don't you ask for clarifications and after getting that, you can suggest as many suggestions as you would like to!
Otherwise, your suggestions go waste, if the askers intention was different!

You can try this approach.
You will have to work backwards.
get the current time using time function and store it in t1:
t1 = time(NULL);

Next, you have to find out how many seconds have elapsed in last 24 months. (If it is always multiple of 12, then it will be easier. If not then you will have to keep count of the number of days in each month).
So, you will have to try to find out, if the last year and the one previous to that was a leap year.
If it is leap year, then no of days will be 366, otherwise 365.
now t2 = no_of_days * 24 * 60 * 60;

If you are not concrened about the exact day, then it is very easy!
date = 20040416;
Divide this to 3 parts day, month and year. (For this you will have to write a small function, which I think you can write)
After calling that function, it will become:
day = 16;
month = 4;
year = 2004;
You you want to go back 24 months.
So do like this:
new_day = day;
new_month = month - 24;
New_year = year;
if (new_month == 0)
{
new_month = 12;
new_year--;
}
else if (new_month < 0)
{
while (new_month < 0)
{
new_month = new_month + 12;
new_year = new_year - 1;
}
}

An Outlet in Cocoa is a persistent reference to a GUI control; it connects a property (a variable) to a control. For example, it is common to create an Outlet for the text field GUI control and change the text that appears in this field via that Ou…

Preface
I don't like visual development tools that are supposed to write a program for me. Even if it is Xcode and I can use Interface Builder. Yes, it is a perfect tool and has helped me a lot, mainly, in the beginning, when my programs were small…